1. Field of the Invention
The present invention relates to a sheet type heat pipe for efficiently cooling high heat generating components such as semiconductors, and particularly to a sheet type heat pipe for efficiently cooling a semiconductor or the like which is mounted in an extremely thin housing.
2. Related Art
Recently, built in electronic equipment is a component with high power and high density, such as a micro processor. As a micro processor becomes extremely higher in density and performs processing such as computing and control at high speed, it generates a large amount of heat. In order to cool such a component with high power and high density like a semiconductor chip, there have been proposed various cooling systems. One of typical cooling systems is a heat pipe.
Heat pipes take various shapes, including a round-pipe type (cylindrical) heat pipe and a plate type heat pipe. Preferably used to cool a component to be cooled of an electronic device such as a CPU is a plate type heat pipe because the plate type heat pipe can be readily mounted onto the component to be cooled and can assure a large contact surface therewith.
Further, heat pipes are classified by a position where a component to be cooled is mounted, that is, whether the component to be cooled is mounted on the upper side of a heat pipe (Top Heat Mode) or lower side of a heat pipe (Bottom Heat Mode). For the Bottom Heat Mode, a fluid circulates by the gravity. On the other hand, for the Top Heat Mode, a fluid must be circulated against the gravity, usually by way of capillary action of a wick.
A space is provided in a heat pipe to be used as a fluid path for a working fluid. The working fluid in the space changes its phase by evaporation, condensation and the like and is moved. Such phase transformation and movement of the working fluid allows heat to be moved.
Detailed description is made below about a heat pipe which has a hermetically sealed cavity and allows heat to be transferred by phase transformation and movement of a working fluid contained in the cavity
At a heat absorbing side of the heat pipe, heat generated by a component to be cooled and conducted in a material of a container of the heat pipe is absorbed as latent heat to vaporize a working fluid. The vaporized working fluid is moved to a heat dissipating side of the heat pipe. At the heat dissipating side, the vaporized working fluid is condensed to release a latent heat and to become liquid again. Then, the liquefied working fluid flows back to the heat absorbing side (circulation). Such phase transformation and movement of the working fluid allows heat to be moved.
For a gravity type heat pipe, a working fluid which becomes liquid by phase transformation is moved (circulated) to the heat absorbing side by the gravity.
In these days, a housing in which an above-described chip or the like is mounted becomes thinner little by little, and a heat pipe correspondingly becomes thinner.
A sheet type heat pipe is disclosed in a Japanese Laid-Open Patent Publication No. 2001-165584 (which is hereinafter referred to as “related art”. In the related art, a plurality of columnar spacers jointed to a container.
However, a sheet type heat pipe of the related art presents the following problems.
One of them is that spaces between columnar spacers are uneven, which may exhibit a wide range of performance, lacking in reliability. Next, since columnar spacers are jointed to a container by an adhesive agent or the like, noncondensable gas is generated within the container, which may impair the long-term reliability. Further, when a main body of the container is bent, a jointed columnar spacer is fallen off the container, which may deteriorate performance. Furthermore, the individual difference may be larger among the products. Another problem lies in that a large number of components and steps are required.
Further, when a foil for forming a container is thinner to reduce the thickness, the own strength of the foil is significantly lowered. Then, a recess occurs along the fluid path by ambient pressure, the fluid path becomes narrower, causing accumulation of the fluid to block the fluid path. Furthermore, there occurs irregularity in the surface of the container, raising a problem that the container surface in contact with a component to be cooled is reduced.